1. vB isn’t free (obvious one I know)
2. vB skinning is difficult and often good skins cost money
3. vB has a bloated system and you can’t remove parts you don’t need
4. vB upgrading is an incredible hassle while MyBB has a near perfect upgrade system
5. MyBB has an excellent plugin system that if used properly requires no core file changes
6. Tikitiki is cool
7. MyBB has been steadily advancing it’s code base for resource efficiency
8. MyBB requirements are less than vB allowing for smaller sites to thrive on cheap hosts
9. AJAX features…yes I know vB has some too but MyBB uses them with efficiency and sensability
10. Quick learning curve and vB is a nightmare to understand. There are dozens of settings in vB that are plain ridiculous
11. Fast easy install…yes you do this normally just once but MyBB makes it really easy

Now in turn I ask you, what made you choose MyBB over another bulletin board software?